The present disclosure relates to a power inductor, and more particularly, to a power inductor having excellent inductance characteristics and improved thermal stability.
A power inductor is generally provided on a power circuit such as a DC-DC converter provided in portable devices. The power inductor is being increasingly used instead of an existing wound type choke coil pattern due to the tendency toward the high frequency and miniaturization of the power circuit. Also, the power inductor is being developed for miniaturization, high current, and low resistance as small-sized and multifunctional the portable devices are required.
The power inductor may be manufactured in the form of a stacked body in which ceramic sheets formed of a plurality of ferrites or a low-k dielectric are stacked. Here, a metal pattern is form in a coil pattern shape on each of the ceramic sheets. The coil patterns formed on the ceramic sheets are connected to each other by a conductive via formed on each of the ceramic sheets and have a structure in which the coil patterns overlap each other in a vertical direction in which the sheets are stacked. Typically, a body of the power inductor is manufactured by using a magnetic material including a quaternary system of nickel, zinc, copper, and iron.
However, since the magnetic material has a saturation magnetization less than that of a metal material, it may be difficult to realize high current characteristics that are recently required for portable devices. Thus, since the body of the power inductor is formed of metal powder, the saturation magnetization may increase in comparison with a case in which the body is formed of a magnetic material. However, when the body is formed of a metal, a loss of material may increase due to an increase in loss of eddy current and hysteria in a high frequency. To reduce the loss of the material, a structure in which the metal powder is insulated from each other by using a polymer is being applied.
However, the power inductor including the body formed of the metal powder and polymer may decrease in inductance due to an increase in temperature. That is, the power inductor increases in temperature by heat generated from portable devices to which the power inductor is applied. As a result, while the metal power forming the body of the power inductor is heated, the inductance may decrease.